Three-phase claw-pole generators having a passive rectifier bridge may be used to generate power in 14 V vehicle electrical systems. In the case of a load dump (a sudden drop in load), which is produced for example by quickly cutting off a high load current, a high free-running voltage occurs at the generator output, due to a delayed response on the part of the generator output voltage regulator. To avoid overvoltage damage in vehicle electrical systems, this overvoltage must be limited. Zener diodes may be used for this purpose in general rectifiers, which may be an economical approach to this problem. The rectifier diodes, i.e., Zener diodes, are used during normal operation to rectify the alternating phase voltage produced by the generator. In this case, the Zener diodes are operated in the forward direction and have a current flowing from the anode to the cathode.
In 14 V vehicle electrical systems, the rectifier Zener diodes meet certain tolerance conditions, the maximum voltage tolerated by the electrical system from the generator, in extreme cases, being double the normal electrical system voltage or even higher. These ratios may not be easily transferable to vehicle electrical systems having higher supply voltages because doubling this high supply voltage would result in such a high voltage that further protective measures would be required.